Structure of visible and dark matter components in spiral galaxies at redshifts z = 0.5{-0.9}

Abstract

We have constructed self-consistent light and mass distribution models for four disk galaxies at redshifts z=0.48, 0.58, 0.81 and 0.88, using the HST archive WFPC2 observations (HDF-S, MDS, Groth Strip survey) and rotation curves measured by Vogt et al. ([CITE]) and Rigopoulou et al. ([CITE]). The models consist of three components: a bulge, a disk and a dark matter halo. Similarly to the sample studied in Paper I (Tamm & Tenjes [CITE]), light distribution of the galaxies in the outer parts is clearly steeper than a simple exponential disk. After applying k-corrections, calculated mass-to-light ratios for galactic disks within the maximum disk assumption are M/L_B = 0.9, 7.4, 4.3 and 1.4, respectively. Together with the galaxies from Paper I, the mean < M/L_B> = 2.5 at < z> ≃ 0.9, indicating no significant evolution of M/L_B with redshift. Central densities of dark matter halos for an isothermal model are 0.008, 0.035, 0.013, and 0.022 in units M_⊙ /pc^3, respectively. Together with the galaxies from Paper I, the DM central density of the four galaxies at mean readshift < z> ≃ 0.9 is ρ (0) = (0.012{-}0.028) M_⊙/pc^3, also showing no significant evolution with redshift. We have also constructed mass distribution models without assuming flat rotation curves and without a dark matter component. Due to the limited extent of the observed rotation, the models without a dark halo nearly fit the observations. In this case, mass-to-light ratios for the galactic disks are 1.8, 9.7, 12. and 1.9, respectively.